Prefabricated fireplace particles

ABSTRACT

A lightweight prefabricated masonry/steel kiva-style fireplace. The firebox is cast in three or more modular sections. The entire inner combustion chamber is lined with split refractory firebrick and an outer shell is lightweight vermiculite concrete. The center firebox section has a semi-circular concave interior and the tubular steel and mesh exterior kiva fireplace stuccoed and plastered frame facade has a semi-circular convex exterior configuration with the appearance of a sculpted adobe fireplace. The firebox damper/anchor plate provides a transition from the masonry firebox to a double-walled chimney system. The firebox can be placed in a room comer or in a chase on a flat wall. It can also be installed over wood floors, in old or new construction.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of co-pending U.S. patent application Ser. No. 09/627,183, entitled “Kiva Fireplace,” filed on Jul. 27, 2000, and the specification thereof is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention (Technical Field):

[0003] The present invention relates to fireplaces, particularly to a lightweight prefabricated fireplace for residential or small business installation.

[0004] 2. Background Art:

[0005] Fireplaces are popular features for homes and small businesses. In some locations, a fireplace may serve as a significant or supplemental source of building heat in colder climes. Further, a fireplace may be a centerpiece of room decor, and when in use may improve the ambiance and mood of the room. In the western United States, especially the southwestern United States, a particular style of fireplace sometimes called a “kiva” fireplace has become popular. Kiva-style fireplaces are patterned after the fireplaces used by ancient and modem Native Americans (particularly the Pueblo and Hopi peoples). A kiva fireplace features gentle, rounded exterior contours and a relatively small fireboxes with a rounded concave interior combustion chamber. A kiva-style fireplace typically has a generally cylindrical chimney of modest diameter that is visible within the interior of the room.

[0006] Currently, fireplaces, particularly kiva-style fireplaces, ordinarily are constructed with the construction of the building. They usually are constructed from relatively heavyweight materials, e.g., adobe bricks, stones, masonry and mortar, and the like. While such “original installation” kiva fire places are durable and handsome, their character, particularly their weight, normally requires that the building be specially designed to accommodate them. A conventional kiva fire place generally cannot be “retrofitted” into an existing structure, especially on an upper story or floor, at least not without extensive structure remodeling.

[0007] A variety of fireplace types are disclosed in the following patents, which offer background in the art: U.S. Pat. No. 6,109,257 to Hodge et al.; U.S. Pat. No. 4,422,438 to Scholtz et al., U.S. Pat. No. 5,168,862 to McGee; U.S. Pat. No. 5,052,3112 to Kincaid

[0008] A need remains for a lightweight, prefabricated fireplace, especially a kiva-style fireplace, that can be easily installed into existing structures, such as the room of a residence.

SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)

[0009] A lightweight prefabricated masonry/steel kiva-style fireplace. The firebox is cast in three or more modular sections. The entire inner combustion chamber is lined with split refractory firebrick and an outer shell is lightweight vermiculite concrete. The center firebox section has a semi-circular concave interior and the tubular steel and mesh exterior kiva fireplace stuccoed and plastered frame facade has a semi-circular convex exterior configuration with the appearance of a sculpted adobe fireplace. The firebox damper/anchor plate provides a transition from the masonry firebox to a double-walled chimney system. The firebox can be placed in a room corner or in a chase on a flat wall. It can also be installed over wood floors, in old or new construction.

[0010] There is provided according to the invention a modular fireplace apparatus comprising a firebox and a facade. The firebox comprises a base; a central body comprising pre-cast vermiculite concrete, disposable upon said base, and comprising an inner body wall defining and partially surrounding a combustion chamber, said inner body wall also at least partially defining a box aperture opening into said combustion chamber; and a smoke plenum section disposable upon said central body, and comprising an inner plenum wall. The facade is locatable around said firebox to at least partially surround and enclose said firebox, said facade comprising a lightweight frame, and said frame defining a facade aperture. The base, central body, and plenum section are modular, and said facade access opening is alignable with said box aperture to permit access through said facade into said combustion chamber, and said central body connectable to said base and said smoke chamber connectable to said central body by refractory mortar.

[0011] The base preferably comprises pre-cast vermiculite concrete, and in the preferred embodiment is generally planar, having sides and a back defined by a single wall defining a substantially arcuate plan profile. The central body preferably comprises an outer shell comprised of vermiculite concrete. The inner body wall of the central body preferably comprises a substantially arcuate plan profile. A plurality of lightweight split refractory bricks preferably are mounted upon said inner body wall.

[0012] The apparatus preferably includes a combustible air flume, attached to said base proximate to said box aperture when said firebox is in use, for drawing air toward said combustion chamber. The flume is a vented conduit, and may feature some means (such as a hinged door) for closing a vent in said conduit when said apparatus is not in use.

[0013] In some embodiments, the inner plenum wall at least partially defines an upper portion of said box aperture, so that both the smoke plenum portion and the central body portion define the size and shape of the box aperture through which the combustion chamber is accessed.

[0014] According to another embodiment of the invention, there is provided a modular fireplace assembly comprising a firebox comprising: a base comprising pre-cast vermiculite concrete; a pre-cast vermiculite concrete central body, stackable upon said base and connected to said base when said firebox is in use, and comprising an inner body wall defining and partially surrounding a combustion chamber, said inner body wall also at least partially defining a box aperture opening into said combustion chamber; and a smoke plenum section stackable upon said central body and connected to said central body when said firebox is in use, and comprising an inner plenum wall, wherein said inner plenum wall at least partially defines an upper portion of said box aperture; and a facade locatable around said firebox, and at least partially surrounding and enclosing said firebox when said firebox is in use, said facade comprising a lightweight tubular steel frame, said frame defining a facade aperture. In this embodiment, the facade aperture is alignable with said box aperture to permit access through said facade into said combustion chamber when said firebox is in use.

[0015] Again, the base is generally planar, having sides and a back defined by a single wall defining a substantially arcuate plan profile.

[0016] The central body preferably comprises an outer shell comprised of vermiculite concrete, and the inner body wall thereof preferably comprises a substantially arcuate plan profile. A plurality of lightweight split refractory bricks are mounted upon said inner body wall.

[0017] Still further, there is provided according to the invention a method of assembling a lightweight modular fireplace comprising the steps of assembling a firebox, fashioning a facade frame, locating the facade frame around the firebox, thereby at least partially surrounding and enclosing the firebox; and covering the facade frame with a stucco. The step of assembling the firebox includes the steps of (1) pre-casting a base of vermiculite concrete and refractory bricks; (2) pre-casting a central body of vermiculite concrete and refractory bricks; (3) stacking the central body upon the base and connecting the body to the base prior to using the firebox, the firebox partially surrounding a combustion chamber; and (4) stacking a smoke plenum section of pre-cast vermiculite and refractory firebricks upon the central body and connecting the plenum section to the central body prior to using the firebox.

[0018] A primary object of the present invention is to provide a complete fireplace that can be installed with the simplicity of a zero-clearance unit and yet having the appearance of a total custom-built kiva adobe fireplace.

[0019] Another object of the present invention is to eliminate the undesirable cold convection that occurs with conventional masonry fireplaces.

[0020] A primary advantage of the present invention is that it provides a lightweight masonry firebox that can be placed in close proximity to walls containing combustible materials and can be installed over wooden floors.

[0021] Another advantage of the present invention is that it eliminates the need for special footings, such as those required to support the massive wight of typical all-masonry fireplaces.

[0022] Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating a preferred embodiment of the invention and are not to be construed as limiting the invention. In the drawings:

[0024]FIG. 1 is a front view of the firebox component of the fireplace apparatus of the present invention;

[0025]FIG. 2 is a side sectional view of the firebox component seen in FIG. 1, taken along section line 2-2 in FIG. 1;

[0026]FIG. 3 is a plan sectional view, from above, of the firebox component seen in FIG. 1, taken along section line 3-3 in FIG. 1;

[0027]FIG. 4 is another plan sectional view, from above, of the firebox component seen in FIG. 1, taken along section line 4-4 in FIG. 1;

[0028]FIG. 5 is a front, perspective, partially exploded view of the firebox component of the fireplace apparatus of the present invention, showing how a combustion air flume may be attached to the front of the assembled apparatus;

[0029]FIG. 5A is an enlarged perspective view of the combustion air flume element of the invention seen in FIG. 5;

[0030]FIG. 6 is a front perspective view of the facade frame according to the present invention, to approximately the same scale as FIG. 5, the facade frame allowing a facade to surround and enclose the firebox component seen in FIG. 5;

[0031]FIG. 7 is a front view of a completed facade component of the invention, disposed around the firebox component, to provide a completed kiva fireplace according to the apparatus of the present invention; and

[0032] FIGS. 8-10 illustrate various different styles of facade according to the present invention, surrounding a firebox component of the invention, to provide aesthetic, lightweight fireplaces for use.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES FOR CARRYING OUT THE INVENTION)

[0033] Currently, fireplaces are generally of two types: all-masonry fireplaces and steel “zero-clearance” fireplaces. The present invention offers the homeowner or home builder with a lightweight alternative fireplace that may be installed in a wide variety of locations, including the upper floors of existing buildings of two or more stories. While the invention has utility in new construction, it is contemplated that an advantage of the invention is its suitability for use in existing buildings. Thus, the inventive fireplace may be used in either original or “retrofit” installation.

[0034] The invention is a wood burning fireplace that can be converted, if desired, to gas burning (with ceramic logs), without requiring any basic design change. In its preferred embodiment, the inventive apparatus provides the user with an aesthetic southwestern style kiva fireplace and a supplementary heat source.

[0035] The fireplace according to the invention is advantageous over the known art in several respects. It is much lighter than the masonry fireplaces of conventional construction, and requires no special footings. It eliminates cold convection that occurs with solid masonry fireplaces. It can be installed over wood floors in new or existing homes. In contrast with known “zero-clearance” fireplaces, the present invention features a semi-circular firebrick (or lightweight concrete) firebox interior with a lightweight stuccoed tubular steel and mesh frame. The frame of the inventive fireplace permits the unit to have the shape of a traditional kiva fireplace, including an arched firebox opening. In sum, the user can appreciate the aesthetics of a real southwestern kiva fireplace without the disadvantages of an all masonry fireplace or steel zero-clearance fireplace.

[0036] The invention is a lightweight masonry and steel kiva fireplace that may burn either solid fuel, particularly wood, or fluid fuel, such as natural gas or propane. The firebox of the invention may be placed in direct contact or close proximity to combustible building materials, and accordingly may be placed against or close to building walls. The firebox disclosed herein can be used in either new construction or remodeling and in close proximity to the structure's walls. The firebox is zero-clearance in basic type, while the fireplace unit features a double-walled, air-cooled metal chimney system. As mentioned, no special footings are required, so the invention may be installed over wood floors.

[0037] The firebox of the invention is fashioned from refractory firebrick inside the combustion chamber, which in turn is partially surrounded by an outer shell of lightweight concrete. The invention's lightweight facade, which houses the firebox, achieves the appearance of a custom adobe fireplace.

[0038] Attention is invited to the drawing figures, especially FIGS. 1-6, which further illustrate and disclose the invention. The apparatus of the invention includes two major components, the firebox 20 (FIGS. 1-5) and the facade 50 (FIGS. 6 and 7). These elements are manufactured mostly off-site, and largely by pre-casting in vermiculite concrete, and as modular components are transported from the manufacturing facility to the residential or small business job site for installation. The firebox 20 is assembled and secured in place within the structure (e.g. preferably in the comer of a room), and then is covered and surrounded by the facade 50. When the inventive fireplace is completely and properly assembled, the facade 50 substantially surrounds and covers the firebox 20, there being however a volume of air space between the facade and the exterior of the firebox.

[0039] Referring to FIGS. 1-4, it is seen that the firebox 20 features three main sub-components: a base 22, a pre-cast vermiculite concrete central body 24, and a smoke plenum section 26. The base 22, which has a generally semicircular convex exterior back, is placed upon the floor, or on concrete blocks over a wood floor, of the room in which the invention is to be installed. The central body 24 has a concave interior chamber therein and a convex back, as suggested in FIG. 4, and is disposable upon the base 22 before the firebox 20 is useable. The central body 24 has an inner body wall 27 defining and partially surrounding a combustion chamber 28; the combustion chamber is the location of the fire when the completed apparatus is in use. The inner body wall 27 also at least partially defines a firebox aperture 29 opening into the combustion chamber 28. As best seen in FIGS. 1, 3, and 5 , the inner body wall 27 preferably has a substantially arcuate plan profile. In the preferred embodiment, a plurality of lightweight split refractory bricks 34 are cast into the inner body wall 27. As indicated by FIGS. 1-3, the central body 24 and the smoke plenum section 26 have a thick (e.g. 4 inches) outer shell 47 of lightweight vermiculate concrete, preferably reinforced with No. 16 gage 2-inch by 2-inch square grid welded wire screen 49.

[0040] The smoke plenum section 26 is disposable upon the central body 24 when the firebox is in use to contain a flame in the combustion chamber 28. The upper plenum section 26 also has an inner plenum wall 31 confronting and defining the upper bounds of the combustion chamber 28. As seen in FIGS. 1 and 2, in the preferred embodiment, the inner plenum wall 31 at least partially defines an upper portion 45 of the box aperture 29. This upper portion 45 in a kiva style fireplace may be a metal arch, for example, to define the arched firebox opening characteristic of kiva fireplaces (FIG. 7).

[0041] The facade 50 is locatable around the firebox 20 to at least partially surround and enclose the firebox. The facade 50 preferably has a frame 51 crafted from a lightweight steel tubes that have been bended and joined to outline the exterior contours of a typical kiva style fireplace, as best seen in FIG. 6. The frame 51 defines a facade aperture 52 as well as the chimney enclosure 54. An advantage of the present invention is the use of bendable tubing to craft the frame 51, thereby permitting a fireplace facade exhibiting the smooth, graceful curves and rounded contours customarily associated with kiva style fireplaces.

[0042] Because the base 22, central body 24, and plenum section 26 are modular, they can be separately manufactured and transported to the job site, and there stacked one upon the other to assemble the firebox 20 as illustrated in FIGS. 1, 2, and 5. The central body 24 is connectable to the base 22, and the smoke plenum section 26 is connectable to the central body 24 using refractory mortar 36, so that the three main subcomponents of the firebox 20 are securely mortared together in the completed apparatus for use. The assembled firebox 20 is situated so that the central body 24 and plenum section 26 are at least about three inches from the nearest adjacent combustible building materials (e.g. walls). The facade frame 51 may then be placed over the installed firebox 20. The facade aperture 52 has a size and shape generally corresponding to the box aperture 29; these two apertures are alignable to permit access through the facade 50 into said combustion chamber 28 in the completed fireplace assembly, as seen in FIG. 7. With the facade aperture 51 and the box aperture 29 in registration, the edges of the apertures are in close adjacency, and can be sealed with mortar, to provide a integral aperture and to prevent smoke and debris from entering between the firebox and facade. The juncture of the front of the firebox 20 with the front of the facade 50 where the edges of their respective apertures come together, is the only area of substantial contact between the firebox and the facade. The firebox is within, but spaced-apart from, the facade 50.

[0043] To provide a fire-resistant and yet lightweight fireplace, the base 22 preferably is pre-cast of vermiculite concrete. As seen in FIGS. 1 and 3, for example, the base 22 preferably is generally planar, having sides and a back defined by a single wall 32 defining a substantially arcuate plan profile. Similarly, the central body 24 has an outer shell 25 pre-cast or otherwise formed of vermiculite concrete.

[0044] A steel anchor plate and damper assembly 40 is shown in FIGS. 2 and 5. The anchor plate assembly 40 is secured (for example with ⅜-inch×3 inch lag bolts) over a chimney aperture in the top of the plenum section 26 of the firebox. The interior of the damper 41 receives the inner stainless steel chimney 43 of an air cooled steel chimney system 42, thus providing masonry-to-steel chimney connection. The damper 41 is positive open or closed. This is accomplished by a steel bar counter-weight 56. When the damper handle 57 is pushed up, the counter-weight 56 holds the damper plate 58 open. When the damper handle 57 is pushed down, the damper plate 58 closes.

[0045] Referring again to FIG. 6, it is seen that a fireplace facade frame 51 is crafted from tubular steel, for example ½-inch tubes, bent, welded and assembled to achieve the appearance of a southwestern kiva fireplace. A steel diamond mesh lath 60 is attached, as by metal screws, to the frame 51 generally to define the exterior contours of the facade 50. At least one, preferably three or more coats of fiberglass-impregnated stucco 62 is applied to the entire facade 50, with the result that the fireplace obtains the appearance seen in FIG. 7. The frame 51 can be secured to the adjacent interior walls of the building to supply overall stability for the apparatus, the preferred and traditional location of a kiva fireplace being the comer of a room. FIG. 7 depicts the appearance of the completed apparatus, the facade 50 having been secured (e.g. by adhesives and/or screws) in place around the firebox 20 and the chimney system 42. A pleasant transition finish preferably is applied to aesthetically join the edges of the facade 50 to the adjacent walls.

[0046] The facade 50 is completely factory manufactured. The facade 50, with frame 51, is transported to the installation site, and is secured to the firebox and to the site structure (e.g. walls), and then added stucco 62 is applied.

[0047]FIGS. 8, 9 and 10 illustrate additional alternative fireplace designs according to the invention. It will be readily appreciated by one of ordinary skill in the art that the flexibility in design provided by the use of the facade frame 51 permits the inventive apparatus to have a facade 50 manifesting any of a wide variety of custom exterior appearances. All aesthetic designs may be manufactured according to the foregoing disclosure.

[0048] Referring particularly to FIGS. 5 and 5A, the inventive fireplace optionally but preferably includes a combustible air flume 35, attached to the base 22 proximate to the box aperture 29 when the fireplace is completely assembled and the firebox 20 is in use. The flume 35 draws air toward the combustion chamber 28, as further described herein. The flume 35 essentially is a vented conduit, and preferably features some means for closing a vent hole in the conduit when the fireplace apparatus is not in use.

[0049] Referring to FIGS. 5 and 5A, the combustion air flume 35 is mounted to the face of the base 22, halfway below the box aperture 29. This mounting can be accomplished by, for example, angle brackets 64 and #8 x 2V inch screws. The flume 35 is mounted so as to position a vent 37 towards the combustion chamber 28. A hinged vent door 38 is provided upon the flume 35 as a means to controllably open and close the vents 37, the vent apertures preferably being closed when the fireplace is not in use. A handle 63 is mounted upon the vent door 38 for ease and safety of manipulating the door 38. As seen in FIG. 5A, when the vent door 38 is opened, it exposes and uncovers at least one vent aperture, e.g., a pair of vents 37 in the form of two ¾-inch by 15-inch slots in the flume 35; the flume 35 preferably is a conduit crafted from, for example, a length of 2-inch by 2-inch square steel tube with open ends. The door 38 can be a length of right-angle-iron mounted with hinges upon the flume 35. The hinges permit the door to pivot between an open and a closed position; to open, the handle 63 is pushed toward the fireplace (directional arrow in FIG. 5). FIG. 5A shows the flume 35 in an open position; to close, the use can simply pull on the handle 63 to pivot the door 38 forward (directional arrow in FIG. 5A) to rotate the vent door into a position covering the vents 37. A plaster stop and door channel 65 is mounted on the face of the flume 35, and provides a finished edge at the fireplace opening and a slot for screen or glass doors.

[0050] In use, the flume 35 draws air in through its open ends, and delivers the air to the combustion chamber 28 of the firebox 20. An approximately 6-inch diameter vent (not shown) is required in an outside wall of the associated building structure to provide outside air within the interior frame cavity defined by the facade frame 51. Such outside air also provides cooling for the double-walled chimney system 42.

[0051] A door frame and glass and/or screen door (not shown) may be provided in and for the facade aperture 52 generally according to convention to prevent embers from popping from the chamber onto the building floor.

[0052] From the foregoing, it is also evident that the invention includes a method of assembling a lightweight modular fireplace. The method includes the initial step of assembling the firebox 20 by pre-casting the base 22 of vermiculite concrete, and pre-casting the central body 24 of vermiculite concrete. Then, the method includes stacking the central body 24 upon the base 22 and connecting the central body to the base, the firebox 20 partially surrounding the combustion chamber 28, and also stacking the smoke plenum section 26 upon the central body 24 and connecting the plenum section to the central body. Other steps of the method are fashioning the facade frame 51 from tubular steel, locating the facade frame 51 around the firebox 20, thereby at least partially surrounding and enclosing the firebox 20, and covering the facade frame with a stucco, as described above.

[0053] Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of the parent application, and of all patents and publications, cited above are hereby incorporated by reference. 

What is claimed is:
 1. A modular fireplace apparatus comprising: a firebox comprising: a base; a central body comprising pre-cast vermiculite concrete, disposable upon said base, and comprising an inner body wall defining and partially surrounding a combustion chamber, said inner body wall also at least partially defining a box aperture opening into said combustion chamber; and a smoke plenum section disposable upon said central body, and comprising an inner plenum wall; and a facade locatable around said firebox to at least partially surround and enclose said firebox, said facade comprising a lightweight frame, said frame defining a facade aperture; wherein said base, central body, and plenum section are modular, said facade access opening is alignable with said box aperture to permit access through said facade into said combustion chamber, and said central body connectable to said base and said smoke chamber connectable to said central body by refractory mortar.
 2. An apparatus according to claim 1 wherein said base comprises pre-cast vermiculite concrete.
 3. An apparatus according to claim 2 wherein said base is generally planar, having sides and a back defined by a single wall defining a substantially arcuate plan profile.
 4. An apparatus according to claim 1 wherein said central body comprises an outer shell comprised of vermiculite concrete.
 5. An apparatus according to claim 1 wherein said inner body wall comprises a substantially arcuate plan profile.
 6. An apparatus according to claim 5 further comprising a plurality of lightweight split refractory bricks mounted upon said inner body wall.
 7. An apparatus according to claim 1 further comprising a combustible air flume, attached to said base proximate to said box aperture when said firebox is in use, for drawing air toward said combustion chamber.
 8. An apparatus according to claim 7 wherein said flume comprises a vented conduit.
 9. An apparatus according to claim 8 further comprising means for closing a vent in said conduit when said apparatus is not in use.
 10. An apparatus according to claim 1 wherein said inner plenum wall at least partially defines an upper portion of said box aperture.
 11. A modular fireplace assembly comprising: a firebox comprising: a base comprising pre-cast vermiculite concrete; a pre-cast vermiculite concrete central body, stackable upon said base and connected to said base when said firebox is in use, and comprising an inner body wall defining and partially surrounding a combustion chamber, said inner body wall also at least partially defining a box aperture opening into said combustion chamber; and a smoke plenum section stackable upon said central body and connected to said central body when said firebox is in use, and comprising an inner plenum wall, wherein said inner plenum wall at least partially defines an upper portion of said box aperture; and a facade locatable around said firebox, and at least partially surrounding and enclosing said firebox when said firebox is in use, said facade comprising a lightweight tubular steel frame, said frame defining a facade aperture; wherein said facade aperture is alignable with said box aperture to permit access through said facade into said combustion chamber when said firebox is in use.
 12. An apparatus according to claim 11 wherein said base is generally planar, having sides and a back defined by a single wall defining a substantially arcuate plan profile.
 13. An apparatus according to claim 12 wherein said central body comprises an outer shell comprised of vermiculite concrete.
 14. An apparatus according to claim 13 wherein said inner body wall comprises a substantially arcuate plan profile.
 15. An apparatus according to claim 14 further comprising a plurality of lightweight split refractory bricks mounted upon said inner body wall.
 16. An apparatus according to claim 15 further comprising a combustible air flume, attached to said base proximate to said box aperture when said firebox is in use, for drawing air toward said combustion chamber.
 17. An apparatus according to claim 16 wherein said flume comprises a vented conduit.
 18. An apparatus according to claim 17 further comprising means for closing a vent in said conduit when said apparatus is not in use.
 19. A method of assembling a lightweight modular fireplace comprising the steps of: assembling a firebox by: pre-casting a base of vermiculite concrete; pre-casting a central body of vermiculite concrete; stacking the central body upon the base and connecting the body to the base prior to using the firebox, the firebox partially surrounding a combustion chamber; and stacking a smoke plenum section upon the central body and connecting the plenum section to the central body prior to using the firebox; fashioning a facade frame; locating the facade frame around the firebox, thereby at least partially surrounding and enclosing the firebox; and covering the facade frame with a stucco. 